Ask any dermatologist her number-one skin care recommendation, and she’ll probably reinforce what your momma always told you: Wear your sunscreen. Yet startling rates of skin cancer—the most common cancer in the United States, which will strike one in five Americans in her lifetime—indicate the need for deeper understanding of how sunscreen works and which types are most effective. Traditionally, dermatologists have steered people toward chemical sunscreens, which are easily absorbed by the skin and may not effectively shield from UVB and UVA rays, says Denis Dudley, MD, an endocrinologist who has turned his attention to researching and formulating safe sun care products. 

 “Most dermatology literature and the information pamphlets from the professional organizations tend to repeat the industry position that still advocates using soluble filters that give UVB-biased and incomplete protection,” says Dudley. “Rising cancer rates suggest the strategy has failed, and the obvious weak link is the use of sunscreens.”

Experts such as Dudley and consumer health advocacy organizations like the Environmental Working Group (EWG) are helping to change the conversation. They say one of the biggest problems with many sunscreens today is their tendency to focus only on UVB rays (SPF is what tells you UVB protection) but not enough on protecting from UVA rays, which are linked to photoaging and skin cancer. “The global sunscreen market is dominated by UVB-biased sunscreens, particularly in North America,” adds Dudley. “They mostly prevent UVB effects like sunburn to some degree but offer little or no protection against skin cancer or photoaging, where UVA plays a major role.”